Method of broaching



Aug. I1, 1925. 1,549,309

c. w. HOWE ET AL METHOD OF BROACHING Filed April 16, 1925 I Fig.1.

A 5 l ,2 I 7 N OLD PROCESS Patented Aug. 11, 1925.

UNITED STTES EBAY? GHQ CHARLES WARREN HOVJ'E, OF LOWELL, AND HAROLD HOEBER, OF NORTH BILLERICA,

MASSACHUSETTS, ASSIGNOR'S TO BAGS-LOWELL SHOPS, 015 BOSTON, MASSACHU- SETTS, A CORPORATION MASiSACI-IUSET'IS.

METHOD OF BROACI-IING.

T 0 all whom it may 00mm Be it known that we, CHARLES lV. Howe and HAROLD Honnnn, citizens of the United States, residing, respectively, at Lowell, in the county of Middlesex and State of Massachusetts, and at North Billerica, in the county of Middlesex and State of Massachusetts, have invented a new and useful Improvement in Methods of Broaching, of which the following is a specification, like reference characters on the drawings indicating like parts in the several figures.

This invention relates to methods of forming flat sided holes or holes of polygonal cross section in thick metal parts.

An important example of the commercial application of such a process is in the manufacture of the drawing rolls for spinning and drawing frames of the character used in the textile industry. These rolls are connected end to end in the spinning or draw ing frame by means ofshort projections of square cross section, each 'roll having a square hole or socket in one end to receive the projecting square section of the adjoining roll. It has been customary heretofore to make such a hole by first drilling and subsequently broaching with a series of square broaches of gradually increasing dimensions. The same general process is followed in making a hole of polygonal cross section in any thick metal part.

The present invention has for its chief object to improve methods of this character with a view to simplifying this process and producing more accurate results.

Referring to the accompanying drawings,

Figure l is a series of plan views showing successive steps in the process of making a square hole in a piece of metal according to the method usually practiced heretofore;

Fig. 2 is a similar series of views showing successive steps in making a square hole in accordance with one method devised by the present invention;

Fig. 3 is a series of plan views showing successive steps in making a square hole according to another method devised by this invention; and

Fig. 4 is a perspective view of part of a broach.

Referring first to Fig. 1, the metal parts in which the square hole is to be formed is shown at 2. The usual process of forming Serial No. 632,226.

such a hole as heretofore practiced, consists first in drilling a round hole, as indicated at 3, and then forcing a series of square hroaches of successively increased dimen sions through the hole. These broaches are designated at at, 5, 6 and 7, respectively. Each broach is square in cross section and it changes the shape of the hole by removing angular portions therefrom; that is, the first broach forms four corners and each succeeding broach increases the depth of these corners until the final broach '7 completes the operation, forming the entire finished surface. of the hole in this step. It will be understood that in speaking of the finished surfaces of the hole, reference is made to the condition of the surfaces at the completion of the broaching operation. In some instances a further finishing operation of some character may be necessary, but such operations are addi tional to the broaching and the present invention is not concerned with them.

According to one method devised by this invention, the successive steps of which are shown in Fig. 2, a hole 3 is first drilled in the work 2, as in the first step of the prior process above described. A broach 8 is next forced through this hole and produces the flat faces (4, these faces being formed in planes tangent to the round hole 3 and con stituting portions of the finished surface of the broached hole. The next broach. 9 increases the width of the flat faces a and results in forming the wider faces Z). The third broach 10 cuts away still more of the walls of the hole and widens the faces 7) to the extent indicated at c. The final broach 12 cuts out the corners and completes the broaching operation. The general form of this broach is shown in Fig. 4 and it is substantially like the broach 7.

It should be noted that in this process portions of the finished surfaces of the po lygonal hole are formed at each broaching step, the area of these surfaces being increased by the successive breaching operations. It should also be noted particularly that the finished surfaces (4 which are formed by the broach 8 act as guides for the broach 9, while the surfaces 6 formed by the latter broach guide the broach 10. The surfaces 0 formed by the broach 10 also serve as guides for the final broach 12. The finished surfaces formed in each broaching step, therefore, are utilized to guide the tool that performs the next succeeding breaching operation. The guiding of the breaches in this manner isa great advantage in producing a true hole that is; one in which the Walls are all pa 511101 to the axis of the round hole 3 which is formed initially and which is drilled very accurately. i

In the prior process above described. and the steps of which are illustrated in Fig. 1, none of the walls or surfaces are utilized in guiding the breaching tool. -There is always some tendency forthetool to be defiected laterally, with the obvious result that a hole will be formed whichis not true. This danger is practically eliminated by the process illustrated in Fig 2.

The various steps of another process e1nbodying this invention are disclosed in Fig. 3. According to this process the initial step of drilling the hole 3 in the piece of work 2 is exactly the same as in the pro cesses above described. The first broach 14 cuts away material from the walls ofthe hole 3 at diametrically opposite points 6-6. This broach, however, has, surfaces cl-(Z of the same radius as the hole 3 and which,

consequently, are guided by portions of the walls of the round hole, 7. The second and third breaches 15 and 16, respectively, are guided in the same way, the broach 1.5 cutting away still more material, as indicated at the points f-fq while the broaeh 16 completes the formation of two diametrically opposite corners Up to this point all of the broaches have been guided by portions of the wall of the round hole formed in the initial step. Now that the finished corners -9 have been formed, these cor- 11ers are used as guides for the tools that perform the subsequent broaching opera tions as well as by the surfaces formed by preceding broachingoperations. The next broach 17 enlargesthe hole at the points 7a-h and this enlargement is carried still further by the breach 18 and is completed by the broach 19 which is substantially like the broaches 7 and 12.

It should be noted that this process is like that illustrated in Fig. 2 in that portions of the finished surface are formed at each broaching operation; and also, in that each broach is guided by a previously formed surface of the hole.

if care it taken to drill the hole 3 accurately, there is very little danger of the breach being deflected in the subsequent operations. In theproccss illustrated in Fig.7 3 at least half of the surface of each 7 broac-h is utilized in guiding the broach.

It will be understood, of course, that in performing the breaching operation the usual presses or similar machine tools are employed. 7 it Having thus described our invention, what we desire to claim as new is:

1. That improvement in the method of making holes of polygonal cross section in metal parts, which consists in drilling): a round hole in the worlr. then enlarrgirn said hole to the desired shape by a series of broaching operations, guiding; the breachinp; tool by portions of said round hole until part of the finished hole is formed, and then guidinganother broaching tool by said fin ished surface to effect a further shaping of the hole. I y i i 2. That improvement in the methodof making holes of polygonal cross section in metal parts. which consists in drilling a round hole in the worlr. then enlarging said hole to the desired shape by a series of broachinrz operations, guiding the broach' in stool by portions of said round hole until diametrically opposite corners of the fin ished hole are formed, and then guiding the broachinp; tool b said corners while the shaping of the hole is being completed.

3. That improvement in the method of making: holes of polygronal cross section in metal parts, which consists in drillin a round hole in the work. then enlarging said hole to the desired shape by a series of broaching operations, guiding the breaching tool by portions of said round hole until part of the finished hole is formed, and utilizing the surface formed by each operation to guide the tool used in performing the next operation.

In testimony whereof we have hereunto signed this speclfication.

CHARLES WARREN HOWE. HAROLD HOEBER.

Consequently,

y on

Certificate of Correction.

It is hereby certified that in Letters Patent No. 1,549,309, granted August 11, 1925, upon the application of Charles Warren Howe, of Lowell, and Harold Hoeher, of North Billerica, Massachusetts, for an improvement in Methods of Broaching, an error appears in the printed specification requiring correction as follows: Page 2, lines 42 and 43, strike out the Words as well as by the surfaces formed by preceding broaching operations and insert the same to follow after the Word step and before the period in line 38; and that the said Letters Patent should be read With this correction therein that the same may conform to the record of the case in the Patent Otfice.

Signed and sealed this 22d day of September, A. D. 1925.

[SEAL] KARL FENNING,

Acting Commissioner of Patents. 

